The present invention generally relates to rock crushers. More specifically, the present invention relates to an anti-spin mechanism having a torque limiter for use on a conical rock crusher.
Rock crushers, such as cone crushers, generally include an eccentric assembly that rotates about a main shaft and imparts gyratory motion to a head assembly. Material to be crushed is loaded into a feed hopper that feeds into a bowl assembly. The material, generally rock, is crushed between a bowl liner disposed in the bowl assembly and a mantle on the crusher head assembly.
To crush rock between the head assembly and the bowl assembly, gyratory motion is imparted to the head assembly to alternately widen and narrow the gap between the head assembly and bowl assembly. The gyratory motion may be imparted via an eccentric that rotates with respect to a stationary shaft and directly imparts the eccentric motion to the head assembly. Alternatively, an eccentric assembly may be used to impart gyratory motion to a movable shaft, which in turn imparts gyratory motion to the head assembly. In either case, a frame supports the shaft and head assembly, and a countershaft or other driving mechanism is utilized to drive the eccentric assembly.
The eccentric generally rotates at a high rate of speed (e.g., 200 rpm). Although the interface between the eccentric and the head is lubricated and generally includes a bushing disposed between the two components, without counteracting forces preventing the movement, the head tends to rotate along with the eccentric.
When the crusher is operating and crushing rock (at-load), the head rotates slowly in a direction opposite to the eccentric direction of rotation due to the countervailing forces of the material being crushed. However, during no-load operation (eccentric rotating but no rock being crushed), the head tends to rotate in the direction of the eccentric. Such rotation is not desirable because rock can degrade the crushing surface of the head as the head transitions from rotating in the direction of the eccentric during no-load operation to the opposite rotation of normal crushing operation. Further, improper introduction of rock into a machine can cause ejection of the rock from the machine when the head is rotating at a high rate of speed.
Certain rock crushers include an anti-spin mechanism to prevent undesirable rotation during no-load conditions. The anti-spin mechanism may be a one-way clutch, such as a backstop clutch, that prevents rotation of the head in the direction of eccentric travel but permits travel of the head in the opposite direction during normal crusher operation.
During certain operational circumstances, a large torque driving the head in the direction of eccentric travel may be encountered. For example, a head bushing may fail, thus causing substantial friction between the head and eccentric, forcing the head to travel in the direction of the eccentric. Further, during no-load operation, a rock may fall between the head and bowl and impart a crushing force on the head that has a component in the direction of eccentric travel. Moreover, during at-load crushing operations, certain rock configurations may be encountered that result in a large torque on the head being generated in the direction of the eccentric. In all of these circumstances, a backstop clutch may be at risk for rupture, as the backstop clutch is designed to prevent the head from rotating in the direction of the eccentric during no-load operation, but is not designed to withstand excessive reverse torque loads. Even if the backstop clutch does not fail, other crusher components are at risk for damage due to the unusual torque load.
There is no backstop clutch design for use in rock crushers that has free motion in one rotational direction and a friction clutch torque limit to prevent excess torque in the locked direction. Even if a backstop clutch were designed to incorporate such functionality, the head would have to be removed to service the device. Replacing the backstop clutch with a friction plate torque limiting clutch would be disadvantageous because of the continuous rotation present during at-load operation. The continuous rotation would cause excessive wear on the clutch, resulting in an unacceptably short component service life.
Secondary mechanisms such as shear pins can be utilized to protect the one-way backstop clutch. However, the available space within the head assembly of a conventional rock crusher is limited, presenting design challenges for the device utilized to protect the one-way clutch.
Certain conventional crusher designs utilize shear pins or bolts to protect the backstop clutch. The shear pins permit rotation of the head in the direction of the eccentric by shearing off in response to unusually large torque events in the direction of the eccentric, thus protecting the backstop clutch and other crusher components. However, the utilization of shear pins to protect the one-way clutch presents operational difficulties, as failed shear pins must be replaced after each occurrence of an excessive reverse torque loading. The increased crusher inoperability adds to the overall operation and maintenance costs of a crusher installation.
Another method of protecting the one-way clutch utilizes a torque limiter coupled to the clutch. U.S. Pat. No. 4,666,092 to Bremer, issued May 18, 1987, discloses such a device. The Bremer device utilizes a resetting torque limiter that permits rotation of the crusher head in the direction of the eccentric in the case of excessive torque on the clutch. Thus, the Bremer design eliminates the necessity of shear pins.
During normal operation, the Bremer torque limiter prevents rotation of the crushing head relative to the one-way clutch by utilizing a number of balls forced into corresponding detents by compression springs. Upon an overload exceeding the torque limit of the torque limiter, the balls are forced out of the detents and the torque limiter permits rotation of the head relative to the one-way clutch until the balls are reset into the detents.
A disadvantage of the Bremer device is that the balls may snap into and out of the detents several times before the torque limiter resets, causing multiple shocks to the crusher drive train before the balls properly reset and prevent rotation of the head relative to the one-way clutch. Further, the Bremer device does not continuously dissipate energy to slow down head travel in the direction of the eccentric in the case of unusual torque loadings, as the torque limiter is not a friction clutch device. Accordingly, once the Bremer device begins to rotate, the crushing head may not stop spinning until the crusher is placed at load for a period of time to allow the device to reset. A further disadvantage of the Bremer device is that both the one-way clutch and torque limiter are coupled to the head, such that both devices gyrate along with the head, which can prevent proper engagement of the springs in the one-way clutch.
U.S. Pat. No. 4,206,881 to Werginz, issued Jun. 10, 1980, utilizes a hydraulic motor as an anti-spin mechanism. The hydraulic system does not require shear pins or a torque limiter. Instead, the hydraulic motor is designed to rotate in the direction of the eccentric in the case of a reverse torque overload. However, the hydraulic system requires additional hydraulic components, adding size, expense and complexity to the anti-spin mechanism.
Accordingly, there is a need for a rock crusher that includes an anti-spin mechanism that does not utilize shear pins to protect a one-way clutch. Further, there is a need for an anti-spin mechanism that does not utilize a hydraulic motor or pump. Further still, there is a need for an anti-spin mechanism that permits the one-way clutch to remain stationary during normal crusher operation, rather than gyrating along with the crusher head. Further still, there is a need for an anti-spin mechanism that includes a torque limiting mechanism that both protects the one-way clutch and fits into the small space allowed within the crusher head assembly. Yet further still, there is a need for a device to protect a one-way clutch that provides continuous braking once an excessive reverse torque loading passes, to dissipate the energy of the rotating head and bring the head to a stop.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.
One embodiment relates to a cone crusher. The cone crusher includes a frame, a shaft supported by the frame, and a head disposed on the shaft. An eccentric mechanism is coupled to the head and a one-way clutch is coupled to the shaft. A friction torque limiting clutch is disposed within the head and is coupled between the head and the one-way clutch.
Another embodiment relates to an anti-spin mechanism for a rock crusher having a head, an eccentric, and a shaft. The anti-spin mechanism includes a one-way clutch coupled to the shaft. The one-way clutch permits rotation of the head in a first direction and inhibits rotation of the head in a second direction. A friction torque limiting clutch is disposed within the head and is coupled to the one-way clutch. The friction torque limiting clutch protects the one-way clutch by permitting rotation of the head in the second direction in the case of an excessive torque load.
A further embodiment relates to a rock crusher having a stationary shaft and a head coupled to the shaft. The head is driven in a gyratory manner by an eccentric. A lower spindle extends from the shaft, and a backstop clutch is coupled to the lower spindle. An upper spindle is coupled to the backstop clutch, and a friction torque limiting clutch is coupled between the upper spindle and the head.
A still further embodiment relates to a rock crusher having a head and a stationary shaft. The rock crusher includes means coupled between the head and the shaft for permitting rotation of the head in only one direction. The rock crusher further includes means for limiting the torque on the means for permitting rotation of the head in only one direction. The means for limiting the torque includes a number of plates that frictionally engage one another.
A still further embodiment relates to a method of performing maintenance on a rock crusher having a one-way clutch coupled to a torque limiter disposed within a head assembly beneath a feed plate and a top plate. The top plate is fastened to the head assembly and the torque limiter. The method includes the steps of removing the feed plate, unfastening the top plate from the head assembly, and lifting the torque limiter out of the head assembly.
Alternative embodiments of the invention relate to other features and combinations of features as may be generally recited in the claims.